The present invention relates to a tool for driving headed fasteners, and more particularly, to a socket type tool or a nutsetter.
When loosening or tightening headed fasteners, it is desirous to remove or tighten the fastener without marring or destroying the head. Generally, fastener heads are six-sided and known in the field as hex heads. When tightening a hex head, it is important to apply a force near but not at the vertices of adjacent flat sides. This prohibits the rounding of the vertices and thus enables the hex head to be easily turned by a nutsetter or the like.
Various tools exist in the art for tightening hex heads. The following United States patents illustrate various designs for accomplishing the tightening or loosening of the hex heads. These United States patents define different surfaces to position around and exert a force on the hex heads. These tools are illustrated by U.S. Pat. Nos. 4,581,957; 5,481,948; 4,882,957; 5,012,706; 5,284,073; 5,131,312; 4,512,220; 5,092,203; 4,930,378; 4,598,616; 4,765,211; 5,219,392; and 5,388,486. While these tools appear to work satisfactorily for their intended purpose, inventors strive to improve the art.
The present invention provides the art with a tool that provides clearance for the vertices of the hex heads. The tool bore, at the intersection of the flat surfaces, reduces stress concentrations and thus reduces the possibility of bursting a female socket. The present invention has a contact surface which provides an enhanced mechanical advantage. The present invention provides a tool with a contact face that exerts equal force in both directions of rotation. The tool also contacts the hex heads away from its vertices to reduce the possibility of rounding the polygonal shape of the hex head.
In accordance with one aspect of the invention, a tool for driving headed fasteners comprises an opening in the tool. The opening is defined by a wall of the tool. The wall has a plurality of planar or flat surfaces which are connected to one another by connecting surfaces at their ends to define the opening. Each connecting surface has a convex surface continuous with the planar surface. Also, a concave surface is continuous with the convex surfaces. The concave and convex surfaces define arcs with the arcs having the same radius. The concave surfaces are symmetric about a central axis of the tool. The convex surfaces intersect the planar surfaces at a tangent point. Also, the convex surfaces intersect the concave surfaces at a tangent point. The convex surface contacts the fastener head such that the contact point is at an angle with respect to a line bisecting the flat surface to the tool center with a line from the contact point to the tool center, the angle being from about nineteen to twenty-three (19xc2x0-23xc2x0) degrees. Further, the radius of the convex and concave surfaces is proportional to a distance between parallel planar surfaces such that the radius is eight (8%) percent of the distance. Also, the concave surfaces are on a circle with the center at the center of the tool. The circle has a diameter which is about 1.178 times the distance between planar parallel surfaces. The contact surfaces apply equal force to the hex head whether the fastener is loosened or tightened.